3.5.7.2 -stable review patch. If anyone has any objections, please let me know.
------------------ From: Jens Axboe <[email protected]> commit a8c32a5c98943d370ea606a2e7dc04717eb92206 upstream. Request based dm attempts to re-run the request queue off the request completion path. If used with a driver that potentially does end_io from its request_fn, we could deadlock trying to recurse back into request dispatch. Fix this by punting the request queue run to kblockd. Tested to fix a quickly reproducible deadlock in such a scenario. Acked-by: Alasdair G Kergon <[email protected]> Signed-off-by: Jens Axboe <[email protected]> Signed-off-by: Herton Ronaldo Krzesinski <[email protected]> --- drivers/md/dm.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/drivers/md/dm.c b/drivers/md/dm.c index 9ff3019..32370ea 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -754,8 +754,14 @@ static void rq_completed(struct mapped_device *md, int rw, int run_queue) if (!md_in_flight(md)) wake_up(&md->wait); + /* + * Run this off this callpath, as drivers could invoke end_io while + * inside their request_fn (and holding the queue lock). Calling + * back into ->request_fn() could deadlock attempting to grab the + * queue lock again. + */ if (run_queue) - blk_run_queue(md->queue); + blk_run_queue_async(md->queue); /* * dm_put() must be at the end of this function. See the comment above -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
